Efficiency of eight modified materials for As(V) removal from synthetic and real mine effluents

摘要

Arsenic (As) contamination is a major problem especially for active gold mine operations. In the present study, eight low-cost materials including biochar (B), Fe-loaded biochar (BF), activated biochar (BC), Fe-loaded activated biochar (BCF and BFC), thermally modified dolomite (MD), wood ash (WA), and modified wood ash (MWA) were comparatively used for the efficiency in As(V) removal from synthetic and real mine effluents, through batch and column testing. Batch adsorption tests were conducted in beakers with a ratio adsorbent material and As(V) synthetic and real solutions of 0.1 g: 10 mL at concentrations of 850 and 300 mu g/L As, respectively. Column adsorption tests were performed in 3 reactors with As(V) concentration of up to 900 mu g/L in contaminated neutral drainage (CND) collected from a local gold mine. Results from batch testing with synthetic effluents showed the best performance for As(V) removal in the following order: MD > WA > BCF > BF > BFC > MWA > BC > B. Consistent findings were obtained in batch and column testing with the real mine effluent. Although iron grafted biochars are good adsorbents, their performance for As(V) removal was limited probably because of the very low As concentration in this study. In the same time, MD was found to be the most efficient material for As(V) removal but the final pH must be monitored and eventually adjusted. As(V) was completely removed by MD in batch testing (99.9%) and column testing (99.6%) after > 112 days to bellow the authorized monthly mean allowed by Canadian discharge criteria. Thus, MD seems to be the most efficient material among the tested ones for the removal of As(V) in batch and column testing from synthetic and mine effluents.